This I Know.
The problem is not in the zero pick up.
If you scope your phase in at the driver pic and compaire it to the actual output from the pic to the gate drivers you will see the occasional "missing phase".
what a bummer this was.

I solved the problem by moving the ADC funtion from the feedback pic to the actual driver pics.

The reason for the "missing phase" was the time it took the feedback pic to SERIN/OUT to pics 1-3. plenty of room and time for pic 1-3 to do the ADC and make adjustments post gate firing.

this worked well for me at 200-2400ADC